Wireless power supply system and wireless power reception device

ABSTRACT

When a vehicle approaches a parking space, a ground controller excites a power transmission coil using an excitation pattern signal containing identification data, and a vehicle controller acquires the identification data from the excitation pattern signal received by at least one of subcoils. Then, a communication unit transmits the acquired identification data to the ground unit. The ground controller pairs the power transmission coil and the power reception coil with each other when the identification data contained in the excitation pattern signal and the identification data transmitted from the vehicle controller match each other. Also, the pairing is canceled if the identification data received by the subcoil provided on the front side and the identification data received by the subcoil provided on the rear side are different from each other.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. application Ser. No.15/301,818, filed Oct. 4, 2016, which is the National Stage ofApplication No. PCT/JP2014/060199 filed on Apr. 8, 2014; the entirecontents of which is incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a wireless power supply system and awireless power reception device for wirelessly supplying power to avehicle equipped with an electric load such as a battery.

BACKGROUND ART

Heretofore, a wireless charge system disclosed in Patent Literature 1has been known which is configured to wirelessly supply power to avehicle equipped with a battery (electric load) to charge the battery.This Patent Literature 1 discloses that, in a case where a plurality ofpower transmission devices are present, a power transmission coil isweakly excited to generate a random signal, which is detected by avehicle, and the vehicle and the power transmission device are pairedwith each other if it is confirmed that the random signals match eachother between the vehicle and the power transmission device.

CITATION LIST Patent Literature

Patent Literature 1: International Publication No. WO2012/042902

SUMMARY OF INVENTION

However, in the configuration in the conventional example disclosed inabove Patent Literature 1, in order to perform the pairing, the vehicleenters and stops in the parking space, and in this state a signalcontaining a random ID pattern is transmitted by the power transmissioncoil and received by the vehicle. For this reason, a problem arises inthat it takes a long time before the vehicle starts to be actuallycharged after stopping in the parking space.

The present invention has been made to solve this problem in theconventional art, and an object thereof is to provide a wireless powersupply system and a wireless power reception device capable of quickpairing with a vehicle entering a parking space.

A wireless power supply system according to one aspect of the presentinvention includes a power transmission device and a power receptiondevice, and the power transmission device includes a power transmissioncoil configured to transmit power, a power-supply control unitconfigured to control power to be supplied to the power transmissioncoil, and a power-transmission-side communication unit configured tocommunicate with the power reception device. The power reception deviceincludes a power reception coil configured to receive power transmittedfrom the power transmission coil and supply the received power to thevehicle as drive force, subcoils provided on a front side and a rearside of the vehicle relative to the power reception coil and configuredto receive, as an excitation pattern signal, power transmitted from thepower transmission coil, a power-reception control unit configured tocontrol power reception of the power reception coil and the subcoils,and a power-reception-side communication unit configured to communicatewith the power transmission device. When the vehicle approaches theparking space, the power-supply control unit performs excitation usingan excitation pattern signal containing identification data. Thepower-reception control unit acquires the identification data from theexcitation pattern signal received by the subcoils, and thepower-reception-side communication unit transmits the acquiredidentification data to the power transmission device. The power-supplycontrol unit pairs the power transmission coil and the power receptioncoil with each other when the identification data contained in theexcitation pattern signal and the identification data transmitted fromthe power-reception control unit match each other. The pairing iscanceled if the identification data received by the subcoil provided onthe front side and the identification data received by the subcoilprovided on the rear side are different from each other.

A wireless power reception device according to one aspect of the presentinvention includes: a power reception coil configured to supply powerreceived to a vehicle as drive force; at least one subcoil provided oneach of a front side and a rear side of the vehicle relative to thepower reception coil and configured to receive, as an excitation patternsignal, power transmitted from the power transmission coil of the powertransmission device; a power-reception control unit configured tocontrol power reception of the power reception coil and the subcoils;and a power-reception-side communication unit configured to communicatewith the power transmission device. When the power transmission deviceis excited using an excitation pattern signal containing identificationdata, the power-reception control unit acquires the identification datafrom the excitation pattern signal received by the subcoils, andtransmits the acquired identification data to the power transmissiondevice.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram showing the configuration of a wireless powersupply system according to an embodiment of the present invention.

FIG. 2 is an explanatory diagram showing the relation between a vehicleand a plurality of parking spaces.

FIG. 3 is a circuit diagram of a power unit, a power transmission coil,a power reception coil, subcoils, and a rectification-smoothing circuitof the wireless power supply system according to the embodiment of thepresent invention.

FIG. 4 is an explanatory diagram showing the arrangement of the powerreception coil and the subcoils of the wireless power supply systemaccording to the embodiment of the present invention.

FIG. 5 is an explanatory diagram showing a data string of a pairingsignal used in the wireless power supply system according to theembodiment of the present invention.

FIG. 6 is a perspective view showing the configuration of the powerreception coil and one of the subcoils used in the wireless power supplysystem according to the embodiment of the present invention.

FIG. 7 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle has approached oneof the parking spaces.

FIG. 8 is a set of waveform charts according to the embodiment of thepresent invention showing voltage received by one of the subcoils andidentification data acquired by the subcoil.

FIG. 9 is the first part of a flowchart showing the procedure ofprocessing by the wireless power supply system according to theembodiment of the present invention.

FIG. 10 is the second part of the flowchart showing the procedure of theprocessing by the wireless power supply system according to theembodiment of the present invention.

FIG. 11 is a flowchart showing the procedure of a received-voltagedetermination process by the wireless power supply system according tothe embodiment of the present invention.

FIG. 12 is a flowchart showing the procedure of a pairing process by thewireless power supply system according to the embodiment of the presentinvention.

FIG. 13 is a flowchart showing the procedure of a pairing process indeparture of the vehicle by the wireless power supply system accordingto the embodiment of the present invention.

FIG. 14 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle is approaching oneof the parking spaces.

FIG. 15 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle is entering theparking space.

FIG. 16 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle has entered theparking space.

FIG. 17 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle is stopped at apredetermined position in the parking space.

FIG. 18 is a set of waveform charts according to the embodiment of thepresent invention showing voltage for excitation of the powertransmission coil and voltage received by one of the subcoils.

FIG. 19 is an explanatory diagram according to the embodiment of thepresent invention showing a state where two adjacent ones of thesubcoils are receiving a pairing signal.

FIG. 20 is a set of waveform charts according to the embodiment of thepresent invention showing changes in the voltages received by two of thesubcoils.

FIG. 21 is a set of waveform charts according to the embodiment of thepresent invention showing a procedure of combining pieces ofidentification data received by the two subcoils to generate combineddata.

FIG. 22 is an explanatory diagram according to the embodiment of thepresent invention showing how received signals received by the twosubcoils are combined.

FIG. 23 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle has entered the twoparking spaces in such a way as to straddle them.

FIG. 24 is a set of waveform charts according to the embodiment of thepresent invention showing pieces of received data received by two of thesubcoils and combined data in a situation where the pieces of receiveddata are different from each other.

FIG. 25 is an explanatory diagram according to the embodiment of thepresent invention showing a state where the vehicle has departed fromone of the parking spaces.

FIG. 26 is a set of explanatory diagrams showing modifications of thesubcoil arrangement.

DESCRIPTION OF EMBODIMENTS

An embodiment of the present invention will be described below withreference to drawings. FIG. 1 is a block diagram showing theconfiguration of a wireless power supply system according to anembodiment of the present invention. As shown in FIG. 1, this wirelesspower supply system includes a plurality of power transmission devices(two power transmission devices 101, 101 a are shown in FIG. 1 as anexample) provided to parking equipment on the ground, and a powerreception device 102 mounted on a vehicle 20.

The power transmission device 101 includes a parking space for parkingthe vehicle 20. The power transmission device 101 also includes a groundunit 51, a power transmission coil 11 installed on the ground of theparking space, and a vehicle detection sensor 33 configured to detectwhen the vehicle 20 approaches the parking space. Note that FIG. 1 showsthe two power transmission devices 101, 101 a as an example. The presentinvention is not limited to this case, but is applicable to cases wherethree or more power transmission devices are provided.

The ground unit 51 includes: a power unit 12 configured to excite thepower transmission coil 11 by causing current to flow therethrough; aground controller 13 (power-supply control unit) configured to controlthe actuation of the power unit 12; and a communication unit 14(power-transmission-side communication unit) configured to performwireless communication with the power reception device 102. The powerunit 12 performs control such that an excitation pattern signal formedby excitation of a certain pattern is transmitted from the powertransmission coil 11. Meanwhile, the power transmission device 101 aalso has a similar configuration, and includes a ground unit 51 a, apower transmission coil 11 a, and a vehicle detection sensor 33 a. Notethat the ground controller 13 can be constructed as an integratedcomputer including a central processing unit (CPU) and storage meanssuch as an RAM, an ROM, and a hard disk drive, for example.

The power reception device 102, mounted on the vehicle 20, includes apower reception coil 21 installed at an appropriate position on thebottom of the vehicle 20, and a rectification-smoothing circuit 22configured to rectify and smooth AC voltage received by the powerreception coil 21. The power reception device 102 further includes avehicle controller 24 (power-reception control unit) configured tocontrol the actuation of the rectification-smoothing circuit 22, abattery 23 (electric load) configured to be charged with the voltagereceived by the power reception coil 21, and a communication unit 25(power-reception-side communication unit) configured to communicate withthe ground unit 51. The power reception coil 21 is disposed at such aposition as to face the above-mentioned power transmission coil 11 whenthe vehicle 20 is parked at a predetermined position in the parkingspace. The power reception coil 21 supplies power it receives to thebattery 23. That is, the power reception coil 21 supplies the receivedpower to the vehicle 20 as drive force.

The power reception device 102 further includes subcoils SC1, SC2, SC3,SC4 installed at the bottom of the vehicle 20. These subcoils SC1 to SC4are configured to receive an excitation pattern signal outputted fromthe power transmission coil 11 and output it to the vehicle controller24 while the vehicle 20 is moved and until the vehicle 20 is stopped atthe predetermined position in the parking space. The arrangement of thesubcoils SC1 to SC4 will be described later. Note that the vehiclecontroller 24 can be constructed as an integrated computer including acentral processing unit (CPU) and storage units such as an RAM, an ROM,and a hard disk drive, for example.

FIG. 2 is an explanatory diagram showing the relation between thevehicle 20 and a plurality of parking spaces 32, 32 a. In thisembodiment, a process of pairing the power reception device 102, mountedon the vehicle 20, and the power transmission device 101, correspondingto the parking space 32, at which the vehicle 20 is to be parked, isperformed through wireless communication between the ground units 51, 51a, provided to at the parking spaces 32, 32 a, and the power receptiondevice 102. The power transmission coil 11 of the power transmissiondevice 101 after being paired with the vehicle 20 is energized totransmit power. The power reception device 102 receives this power andcharges the battery 23 (see FIG. 1), mounted on the vehicle 20.

FIG. 3 is a circuit diagram showing detailed configurations of the powerunit 12, the power transmission coil 11, the power reception coil 21,the rectification-smoothing circuit 22, and the subcoils SC1 to SC4,which are shown in FIG. 1, and peripheral elements thereof. As shown inFIG. 3, the power unit 12 includes an inverter circuit 31 formed of aplurality of switch circuits (such for example as semiconductorelements). Moreover, the on and off of each switch circuit arecontrolled under control of the ground controller 13 (see FIG. 1) suchthat a DC voltage Vin supplied from a DC power source 15 is convertedinto an AC voltage of a predetermined frequency.

A resistor R1 and a capacitor C1 are connected to the power transmissioncoil 11. By applying the AC voltage outputted from the power unit 12 tothe power transmission coil 11 and thereby causing a current to flowtherethrough, the power transmission coil 11 can be set to one of firstexcitation which is excitation for pairing to be described later andsecond excitation which is excitation for positioning of the vehicle 20.Further, if the power transmission coil 11 and the power reception coil21 are situated to face each other as shown in FIG. 1, the powertransmission coil 11 is set to third excitation which is excitation forbattery charging, to thereby wirelessly transmit power for batterycharging to the power reception coil 21.

The power reception coil 21 is connected to a capacitor C2 and aresistor R2, and wirelessly receives the power transmitted from thepower transmission coil 11. The rectification-smoothing circuit 22includes a bridge circuit formed of a plurality of diodes, and acapacitor C3. The rectification-smoothing circuit 22 converts the ACvoltage received by the power reception coil 21 into a DC voltage andfurther smoothes it and then supplies it to the battery 23.

Upon receipt of an excitation pattern signal outputted from the powertransmission coil 11, the subcoils SC1 to SC4 output this excitationpattern signal to the vehicle controller 24, shown in FIG. 1.Specifically, as the vehicle 20 enters the parking space 32, at leastone of the subcoils SC1 to SC4 approaches the power transmission coil 11with the movement of the vehicle 20, and the subcoil SC1 to SC4 thenreceives an excitation pattern signal outputted from the powertransmission coil 11 and outputs this excitation pattern signal to thevehicle controller 24.

FIG. 4 is an explanatory diagram showing the arrangement of the powerreception coil 21 and the subcoils SC1 to SC4, mounted at the bottom ofthe vehicle 20, and the signal receivable range of each of the subcoilsSC1 to SC4. As shown in FIG. 4, the subcoil SC2 is provided on the frontside of the vehicle 20 relative to the power reception coil 21, and thetwo subcoils SC3, SC4 are provided on the rear side of the vehicle 20relative to the power reception coil 21. Further, the subcoil SC1 isprovided at the same position as the power reception coil 21. Thesubcoil SC1 is wound around the same core as the power reception coil21. Specifically, as shown in FIG. 6, the power reception coil 21 ishelically wound around a plate-shaped ferrite core 61, and the subcoilSC1 is also wound around this ferrite core 61 at its substantiallycenter portion.

As shown in FIG. 4, the signal receivable ranges of the subcoils SC1,SC2, SC3, SC4 are denoted by Q1, Q2, Q3, Q4, respectively. If any of thesignal receivable ranges is situated to overlap the excitation range ofthe power transmission coil 11, an excitation pattern signal outputtedfrom the power transmission coil 11 can be received. Here, the signalreceivable ranges of those subcoils adjacent to each other overlap eachother partially. Specifically, the signal receivable ranges Q1, Q2overlap each other partially. Likewise, the signal receivable ranges Q1,Q3, the signal receivable ranges Q1, Q4, and the signal receivableranges Q3, Q4 overlap each other partially. The reason for the partialoverlap between the signal receivable ranges is to prevent disconnectionof the communication of the excitation pattern signal between the powertransmission coil 11 and the subcoils SC1 to SC4 while the vehicle 20 ismoving toward the predetermined position in the parking space 32.

In this embodiment, the power transmission coil 11 is set to the firstexcitation when the vehicle 20 approaches the parking space 32. In thefirst excitation, as will be described later, an excitation patternsignal containing a pairing signal is outputted. Then, pairing isperformed between the power reception device 102 and the powertransmission device 101 based on the pairing signal contained in theexcitation pattern signal received by at least one of the subcoils SC1to SC4. Further, after the pairing is completed, the power transmissioncoil 11 is set to the second excitation and whether or not the vehicle20 is parked at the predetermined position in the parking space 32 isdetermined from the intensity of the excitation pattern signal receivedby the subcoil SC1. Thereafter, if it is determined that the vehicle 20is parked at the predetermined position in the parking space 32, thepower transmission coil 11 is set to the third excitation to wirelesslysupply power.

Here, the power supplied to the power transmission coil 11 in the secondexcitation is higher than the power supplied to the power transmissioncoil 11 in the first excitation. This is to prevent the vehiclecontroller 24 from falsely recognizing that the power transmission coil11 is set to the second excitation while the power transmission coil 11is set to the first excitation.

The first excitation will be described below with reference to a datastring shown in FIG. 5. In the first excitation, the power transmissioncoil 11 is excited in a pattern containing a pairing signal formed of adata string of a start bit, an ID, a data-length code, identificationdata, a sum value, and a stop bit. Thus, the excitation pattern signalto be outputted from the power transmission coil 11 contains the pairingsignal shown in FIG. 5.

In the identification data contained in the pairing signal, a unique bitstring is set which has been assigned to the corresponding parkingspace. For example, “1, 0, 1, 0” is set in the case of four-bit data.The ground controller 13 controls the current flowing into the powertransmission coil 11 such that the pairing signal shown in FIG. 5 can becontained. In sum, in the first excitation, the power transmission coil11 is excited with an excitation pattern signal containing theidentification data.

When a current modulated with the data string of the pairing signalshown in FIG. 5 flows through the power transmission coil 11, thepairing signal is received by the subcoil(s) among the subcoils SC1 toSC4 whose signal receivable range is overlapping the excitation range ofthe power transmission coil 11. This pairing signal is supplied to thevehicle controller 24, shown in FIG. 1.

The vehicle controller 24 reads the data string out of the pairingsignal contained in the excitation pattern signal received by thesubcoil(s) and recognizes the identification data. The vehiclecontroller 24 then transmits the recognized identification data to thecommunication unit 14 through the communication unit 25. If theidentification data transmitted by the power transmission coil 11 andthe identification data received by the communication unit 14 match eachother, the ground controller 13 pairs this parking space and the vehicle20.

Meanwhile, if a plurality of subcoils among the subcoils SC1 to SC4receive data strings, these data strings are ORed. Here, if the datastrings received by the plurality of subcoils are the pairing signaltransmitted from the same power transmission coil 11, ORing them willresult in the same data string. Specifically, if the identification datacontained in a pairing signal is “1, 0, 1, 0” and a plurality ofsubcoils receive this pairing signal, then ORing the identification data“1, 0, 1, 0” contained in each pairing signal will result in “1, 0, 1,0”. Thus, pairing can be performed using this identification data.

On the other hand, if for example the identification data contained in apairing signal received by the subcoil SC3 and the identification datacontained in a pairing signal received by the subcoil SC4 are differentfrom each other, then ORing them will not result in the sameidentification data. For example, if the identification data containedin the pairing signal received by the subcoil SC3 is “0, 1, 0, 1”whereas the identification data contained in the pairing signal receivedby the subcoil SC4 is “1, 0, 1, 0”, then ORing them will result in “1,1, 1,”. This data is invalid data, and the sum value therefore indicatesan error. If the sum value indicates an error, the vehicle controller 24cancels the pairing. Details will be described later.

Next, description will be given of the change in the voltage received bythe subcoil SC2 (the subcoil mounted on the front side of the vehicle20) when the vehicle 20 moves forward and enters the parking space 32between parking lines 34, with reference to an explanatory diagram shownin FIG. 7 and waveform charts shown in FIG. 8. As the vehicle 20 entersthe parking space 32 and the signal receivable range Q2 of the subcoilSC2 partially overlaps the excitation range of the power transmissioncoil 11, the voltage received by the subcoil SC2 gradually rises from atime tO and then drops, as shown in Part(a) of FIG. 8. Once the voltagereceived by the subcoil SC2 exceeds a first threshold voltage Vth1 at atime t1, the data string of the pairing signal can be recognized.Specifically, as shown in Part (b) of FIG. 8, the data string of apairing signal that varies between “0” and “1” is acquired from the timetl. Pairing can then be performed between the vehicle 20 and the parkingspace 32 by using this data string.

Next, description will be given of operation from when the vehicle 20approaches the parking space 32 to when the vehicle 20 stops at thepredetermined position in the parking space 32, with reference to aflowchart shown in FIG. 9 and FIG. 10 and explanatory diagrams shown inFIG. 14 to FIG. 17.

FIG. 14 shows a state where the vehicle 20 is approaching the parkingspace 32 between the parking lines 34. In this state, the groundcontroller 13 is on standby (Step all in FIG. 9) and the vehiclecontroller 24 is approaching the parking space 32 (Step b11). Then, thevehicle controller 24 transmits a wireless signal containing a vehicleID from the communication unit 25 through communication using a LAN(Local Area Network) or the like (Step b12).

Upon receipt of this wireless signal, the communication unit 14 of theground unit 51 recognizes that the vehicle ID contained in the wirelesssignal is a valid vehicle ID (Step a13). Then, the ground unit 51 isactivated (Step a14), and the vehicle controller 24 is notified with awireless signal that the ground unit 51 has been activated (Step a15).

The vehicle controller 24 notifies the driver of the vehicle 20 by meansof a display (not shown) or the like that the ground unit 51 has beenactivated (Step b13). In this way, the driver can recognize that theground unit 51 has been activated. The vehicle controller 24 waits for apairing signal (Step b14).

After the ground unit 51 is activated, the ground controller 13activates the vehicle detection sensor 33 (Step a16). The groundcontroller 13 waits for the vehicle 20 to approach (Step a17).

When part of the vehicle 20 then enters the parking space 32 between theparking lines as shown in FIG. 15 (Step b15), the vehicle detectionsensor 33 detects the entrance of the vehicle 20 into the parking space32 (Step a18). The ground controller 13 sets the power transmission coil11 to the first excitation by using an excitation pattern signalcontaining a pairing signal (Step a19 in FIG. 10). Further, the groundcontroller 13 continues the first excitation (Step a20). At this point,the vehicle controller 24 is waiting for a pairing signal (Step b16).

Then, as shown in FIG. 16, the vehicle 20 approaches the powertransmission coil 11 in the parking space 32 and the signal receivablerange Q4 of the subcoil SC4 reaches such a position as to overlap theexcitation range of the power transmission coil 11 (Step b17). As aresult, the subcoil SC4 receives a pairing signal, and the vehiclecontroller 24 recognizes the identification data contained in thispairing signal (Step b18).

The vehicle controller 24 transmits the recognized identification datathrough the communication unit 25 to request the ground controller 13 toperform pairing (Step b19). Upon receipt of the identification data(Step a21), the ground controller 13 determines whether or not theidentification data contained in the pairing signal transmitted by thefirst excitation and the identification data transmitted from thevehicle controller 24 match each other. If they match each other, thepower reception device 102 and the power transmission device 101 arepaired with each other (Step a22). Details of the pairing process willbe described later. Then, the ground controller 13 startschargeable-position determination control (Step a23).

The vehicle controller 24 recognizes that the pairing has been done(Step b20), and starts chargeable-position determination control (Stepb21).

The ground controller 13 controls the current flowing into the powertransmission coil 11 such that the power transmission coil 11 can be setto the second excitation (Step a24). Then, the ground controller 13shifts to wireless charging (Step a25). The vehicle controller 24determines the level of the voltage received by the subcoil SC1,provided near the power reception coil 21 (Step b22). Details of thisreceived-voltage determination process will be described later.

Then, the vehicle controller 24 shifts to wireless charging (Step b23)if the vehicle 20 is stopped at the predetermined position in theparking space 32, that is, if the vehicle 20 reaches such a positionthat the power transmission coil 11 and the power reception coil 21 faceeach other, as shown in FIG. 17.

Next, a detailed procedure of the received-voltage determinationprocess, shown in Step b22 in FIG. 10, will be described with referenceto a flowchart shown in FIG. 11. When the received-voltage determinationprocess starts, the ground controller 13 sets the power transmissioncoil 11 to the second excitation. Specifically, the ground controller 13excites the power transmission coil 11 with a voltage higher than thatin the above-mentioned first excitation and transmits power from thispower transmission coil 11.

In Step S11 in FIG. 11, the subcoil SC1, provided by the power receptioncoil 21, receives the power generated by the second excitation. Then,the vehicle controller 24 determines whether or not the voltage of thispower has reached a preset second threshold voltage Vth2 (>Vth1).

If the voltage has not yet reached the second threshold voltage Vth2 (NOin Step S12), the vehicle controller 24 determines that the stopposition of the vehicle 20 has not yet reached the predeterminedposition, notifies the driver accordingly in Step S13, and brings theprocess back to Step S11.

On the other hand, if the voltage received by the subcoil SC1 hasreached the threshold voltage Vth2 (YES in Step S12), the vehiclecontroller 24 determines that the vehicle 20 has been reached at thepredetermined position. Then, in Step S14, the vehicle controller 24notifies the driver that the stop position of the vehicle has reached achargeable position, by displaying such information on the display (notshown) or the like. Seeing this display, the driver stops the vehicle20.

In other words, the larger the area of the overlap between the powertransmission coil 11 and the subcoil SC1, the larger the voltagereceived by the subcoil SC1. Thus, by monitoring the voltage received bythe subcoil SC1, it is possible to determine whether or not the vehicle20 is stopped at the predetermined position (chargeable position) in theparking space 32.

In Step S15, the vehicle controller 24 determines whether or not thedriver has inputted a charge start request. If the driver has inputted acharge start request (YES in Step S15), charging of the battery 23 isstarted in Steps a25, b23.

The above processing will be described with reference to Parts (a), (b)of FIG. 18: Part (a) of FIG. 18 is a waveform chart showing the changein the voltage for the excitation of the power transmission coil 11,while Part (b) of FIG. 18 is a waveform chart showing the change in thevoltage received by the subcoil SC1. At a time t0 shown in Part (a) ofFIG. 18, the power transmission coil 11 is set to the first excitation.Specifically, the power transmission coil 11 is excited with anexcitation pattern signal containing a pairing signal. As shown in Part(b) of FIG. 18, the subcoil SC1 receives the pairing signal at the timet0 and the intensity of the received signal rises further, so thatpairing is performed at a time t1. Then, at a time t2, the powertransmission coil 11 is switched from the first excitation to the secondexcitation. Since the vehicle 20 is moving relative to the parking space32, the voltage received by the power reception coil 21 varies as shownin Part (b) of FIG. 18. When the received voltage then reaches thepreset second threshold voltage Vth2, the vehicle 20 is determined tohave reached the chargeable position.

In this embodiment, the description has been given of the example wherewhether or not the vehicle 20 has been stopped at the chargeableposition is determined based on the level of the voltage received by thesubcoil SC1. Note, however, that the present invention is not limited tothis example. Whether or not the vehicle 20 has been stopped at thechargeable position can also be determined based on the level of thevoltage received by the power reception coil 21.

Next, a detailed procedure of the pairing process, shown in Step a22 inFIG. 10, will be described with reference to a flowchart shown in FIG.12.

Firstly, in Step S31, if any of the subcoils SC1 to SC4 is receiving apairing signal, the vehicle controller 24 acquires the identificationdata from the pairing signal. Here, if two or more subcoils arereceiving pairing signals, the vehicle controller 24 acquires combineddata in which the pieces of identification data contained the pairingsignals received by the subcoils are combined with each other.

A method of generating the combined data will be described below withreference to an explanatory diagram shown in FIG. 19 and waveform chartsshown in FIG. 20 and FIG. 21. FIG. 19 is an explanatory diagram showinga positional relation in a state where the vehicle 20 is entering theparking space 32. FIG. 20 is a set of waveform charts showing signalsreceived by the two subcoils SC4, SC1. As shown in FIG. 19, as thevehicle 20 enters the parking space 32 by moving backward as indicatedby arrow Y1 in the figure, the signal receivable range Q4 of the subcoilSC4 firstly overlaps the excitation range of the power transmission coil11. Accordingly, as shown in Part (a) of FIG. 20, the voltage receivedby the subcoil SC4 rises gradually and reaches the first thresholdvoltage Vth1—a voltage that allows communication—at a time t11. As thevehicle 20 further enters the parking space 32, the signal receivablerange Q4 of the subcoil SC4 gradually moves away from the powertransmission coil 11 and therefore the voltage received by the subcoilSC4 starts to drop.

On the other hand, the signal receivable range Q1 of the subcoil SC1,which is wound around the same core as the power reception coil 21 (theferrite core 61 in FIG. 6), overlaps the excitation range of the powertransmission coil 11 after the signal receivable range Q4. Hence, asshown Part (b) of FIG. 20, the received voltage reaches the firstthreshold voltage Vth1 at a time t12. Here, since the signal receivableranges Q1, Q4 partially overlap each other, the voltage received by thesubcoil SC1 reaches the first threshold voltage Vth1 at the time t12,which is before a time t13 at which the voltage received by the subcoilSC4 falls below the first threshold voltage Vth1. In this way, thecommunication with the power transmission coil 11 can be taken over fromthe subcoil SC4 to the subcoil SC1, and the communication can thereforebe prevented from being disconnected in the middle.

This applies not only to the subcoils SC4, SC1. The subcoils SC1, SC2,the subcoils SC1, SC3, and the subcoils SC3, SC4, i.e. the subcoilsadjacent to each other have their signal receivable ranges partiallyoverlapping each other. Hence, it is possible to prevent thecommunication from being disconnected in the middle between the adjacentsubcoils.

Meanwhile, as shown in Part(a) of FIG. 20, the subcoil SC4 can acquireidentification data which varies between “0” and “1”, in the time periodin which its received voltage is above the first threshold voltage Vth1(t11 to t13). Consequently, as shown in Part (a) of FIG. 21, theidentification data is acquired in the time period from the time t11 tothe time t13. On the other hand, as shown in Part (b) of FIG. 20, thevoltage received by the subcoil SC1 reaches the threshold voltage Vth1at the time t12, and the subcoil SC1 can therefore acquire theidentification data at and after the time t12. Consequently, theidentification data is acquired as shown in Part (b) of FIG. 21. Thevehicle controller 24 combines both pieces of identification data togenerate combined data. Specifically, the vehicle controller 24generates the combined data by ORing the identification data acquired bythe subcoil SC4 (the waveform in Part (a) of FIG. 21) and theidentification data acquired by the subcoil SC1 (the waveform in Part(b) of FIG. 21). As a result, combined data shown in Part (c) of FIG. 21is obtained.

In this embodiment, the description has been given of the example wherethe combined data is generated by ORing two pieces of identificationdata, as shown in Parts (a) to (c) of FIG. 21. Note, however, thatcombined data may be generated from a signal obtained by superimposingtwo pieces of identification data. For example, as shown in FIG. 22, ina case where the subcoil SC4 receives a signal indicated by a curve q13and the subcoil SC1 receives a signal indicated by a curve q12, a signalq11 obtained by combining these received signals q12, q13 can becombined data. Specifically, by finding the larger of the receivedsignals q12, q13, it is possible to acquire combined data similar tothat acquired by ORing.

In Step S32, shown in FIG. 12, the vehicle controller 24 computes thesum value of the combined data. Then in Step S33, it is determinedwhether or not the sum value obtained in Step S32 matches the sum valueof the identification data transmitted from the power transmission coil11. If the sum values do not match each other (NO in Step S33), nopairing is performed. If pairing has already been done, this pairing iscanceled in Step S34. Then, the process is brought back to Step S31.

On the other hand, if the sum values match each other (YES in Step S33),the vehicle controller 24 starts pairing in Step S35. In thisprocessing, the data string of the combined data and the data string ofthe identification data transmitted from the power transmission coil 11are compared with each other, and the power reception device 102 of thevehicle 20 and the power transmission device 101 are paired with eachother if the two data strings match each other. Specifically, if forexample the data string of the combined data is “1, 0, 1, 0” and thedata string of the identification data transmitted from the powertransmission coil 11 is “1, 0, 1, 0”, the two data strings match eachother and the power reception device 102 and the power transmissiondevice 101 are therefore paired with each other.

In Step S36, the vehicle controller 24 determines whether or not thepairing has succeeded. If the pairing has not succeeded (NO in StepS36), the process is brought back to Step S31. If the pairing hassucceeded (YES in Step S36), the chargeable-position determinationcontrol is started in Step a23.

Next, detailed description will be given of a case where the combineddata acquired by the vehicle controller 24 and the identification datatransmitted from the ground controller 13 match each other and a casethe where they do not match each other. If the vehicle 20 properlyenters the parking space 32 between the parking lines 34 as shown inFIG. 19, the identification data acquired by each of the subcoils SC1 toSC4 is the same as the identification data transmitted from the powertransmission coil 11.

Then, if combined data is generated by ORing the pieces ofidentification data acquired by the subcoils SC1 to SC4, this combineddata matches the identification data transmitted from the groundcontroller 13. Specifically, as described with reference to Parts (a) to(c) of FIG. 21, if combined data is generated by combining theidentification data received by the subcoil SC4 and the identificationdata received by the subcoil SC1, this combined data matches theidentification data transmitted from the power transmission coil 11.Thus, in the processing of Step S33 in FIG. 12, the sum value of thecombined data is determined to match the other, and therefore pairing isperformed using this combined data.

If the pieces of identification data acquired by the subcoils SC1 to SC4do not match each other, the identification data transmitted from thepower transmission coil 11 and the combined data of the pieces ofidentification data received by the subcoils SC1 to SC4 do not matcheach other, which means an error. This will be described below withreference to an explanatory diagram shown in FIG. 23 and waveform chartsshown in FIG. 24.

Consider a case where the vehicle 20 enters the two parking spaces 32,32 a in such a way as to straddle them, as shown in FIG. 23. In thiscase, the subcoil SC3 receives a pairing signal transmitted from thepower transmission coil 11 in the parking space 32, whereas the subcoilSC4 receives a pairing signal transmitted from the power transmissioncoil 11 a in the parking space 32 a. Consequently, the identificationdata acquired by the subcoil SC3 appears as the waveform shown in Part(a) of FIG. 24, whereas the identification data acquired by the subcoilSC4 appears as the waveform shown in Part (b) of FIG. 24.

Since the two waveforms are different from each other, combined datagenerated by ORing them has an invalid waveform, as shown in Part (c) ofFIG. 24. Hence, in the processing in Step S33 in FIG. 12, the sum valuesare determined not to match each other, and the pairing is canceled.

In sum, if the vehicle 20 enters the two parking spaces 32, 32 a in sucha way as to straddle them, as shown in FIG. 23, pairing is performedwith neither of the parking spaces 32, 32 a. Thus, the driver of thevehicle 20 moves the vehicle 20 and performs operation of entering thedesired parking space.

FIG. 23 has shown the example where the pairing is canceled if thepieces of identification data acquired by the subcoil SC3 and thesubcoil SC4, provided on the rear side relative to the power receptioncoil 21, are different from each other. Note, however, that the pairingis also canceled if the identification data is different between thesubcoil SC2, provided on the front side relative to the power receptioncoil 21, and the subcoil SC3 or SC4, provided on the rear side. That is,the wireless power supply system according to this embodiment cancelsthe pairing if the identification data received by the subcoil providedon the front side relative to the power reception coil 21 and theidentification data received by either of the subcoils provided on therear side relative to the power reception coil 21 are different fromeach other.

Further, the plurality of pieces of identification data may not becombined; the pieces of identification data acquired by the subcoils SC1to SC4 may be compared with each other, and the pairing may be canceledif at least one of the pieces of identification data is different fromthe other pieces of identification data.

Next, description will be given of operation in a situation wherepairing is performed between the power reception device 102 and thepower transmission device 101 but the vehicle 20 then departs from theparking space 32, with reference to a flowchart shown in FIG. 13 and anexplanatory diagram shown in FIG. 25. This operation is performed in asituation where pairing is completed between the vehicle 20 and theparking space 32 but the vehicle 20 then departs from the parking space32 without charging the battery 23, and in other similar situations.

First, in Step S51 in FIG. 13, the vehicle controller 24 waits forcombined data. In Step S52, the vehicle controller 24 determines whetheror not the subcoils SC1 to SC4 have received pairing signals andacquired pieces of identification data. If no identification data isacquired for a certain period of time (NO in Step S52), the pairing iscanceled in Step S53. Then, the process is brought back to Step S51.

On the other hand, if pieces of identification data are acquired (YES inStep S52), the vehicle controller 24 generates combined data in Step S54by ORing the pieces of identification data acquired by the subcoils.

In Step S55, the vehicle controller 24 computes the sum value of thecombined data thus generated. Further in Step S56, it is determinedwhether or not the sum value matches the sum value of the identificationdata contained in the pairing signal transmitted from the groundcontroller 13.

Then, if the sum values do not match each other (NO in Step S56), thepairing is canceled in Step S53. On the other hand, if the sum valuesmatch each other (YES in Step S56), the vehicle controller 24 starts thepairing in Step S57. In Step S58, the vehicle controller 24 determineswhether or not the pairing has succeeded. If the pairing has succeeded,the chargeable-position determination control is started in Step a23(see FIG. 10).

As described above, if the vehicle 20 departs from the parking space 32,the pairing is cancelled as soon as the communication between thesubcoils SC1 to SC4 and the power transmission coil 11 is disconnected.

As described above, in the wireless power supply system according tothis embodiment, the plurality of subcoils SC1 to SC4 are mounted at thebottom of the vehicle 20. Further, as the vehicle 20 approaches theparking space 32, the power transmission coil 11 is set to the firstexcitation and transmits a pairing signal. Furthermore, when at leastone of the subcoils SC1 to SC4 receives this pairing signal, it isdetermined whether the identification data contained in this pairingsignal and the identification data contained in the pairing signaltransmitted from the power transmission coil 11 match each other. Ifthey match each other, the power reception device 102, mounted on thisvehicle 20, and the power transmission device 101 are paired with eachother.

In this way, the vehicle 20 and the parking space 32 can be paired witheach other before the vehicle 20 is stopped at the predeterminedposition in the parking space 32. Hence, it is possible to quicklyperform the chargeable-position determination control and the wirelesscharging, which are executed after the pairing.

Also, at least one subcoil is mounted on each of the front side and therear side relative to the power reception coil 21. Specifically, thesubcoil SC2 is mounted on the front side relative to the power receptioncoil 21, and the subcoils SC3, SC4 are mounted on the rear side relativeto the power reception coil 21. In this way, the identification datatransmitted from the power transmission coil 11 can be received by anyof the subcoils in both of the case where the vehicle 20 approaches theparking space 32 by moving forward and the case where the vehicle 20approaches the parking space 32 by moving backward.

Further, two or more subcoils are provided on at least one of the frontside and the rear side relative to the power reception coil 21.Specifically, the two subcoils SC3, SC4 are provided on the rear siderelative to the power reception coil 21. In this way, once pairing isestablished, it is possible to continue receiving the pairing signaluntil the vehicle 20 then moves and reaches the predetermined positionin the parking space 32.

Also, the signal receivable ranges of the subcoils adjacent to eachother overlap each other partially. In this way, it is possible toprevent the communication with the power transmission coil 11 from beingdisconnected.

Also, if the sum values of the pieces of identification data received bythe subcoils or the sum value of the combined data thereof and the sumvalue of the identification data transmitted from the power transmissioncoil do not match each other, no identification data is transmitted.Specifically, the vehicle controller 24 determines the soundness of thecombined identification data, and does not transmit the combinedidentification data to the ground unit 51 if it is not sound. In thisway, when, for example, pieces of identification data transmitted from aplurality of parking spaces are present together, it is possible toavoid pairing and have the driver recognize that the parked position ofthe vehicle 20 is inappropriate.

Further, the pairing is canceled if the pairing signals received by allthe subcoils SC1 to SC4 are interrupted or if the identification datacontained in the pairing signals becomes mismatched with theidentification data contained in the pairing signal transmitted from theground unit 51. Thus, if the vehicle 20 departs from the parking space32, the pairing is canceled as soon as the communication between thesubcoils SC1 to SC4 and the power transmission coil 11 is disconnected.In this way, the vehicle 20 can instantly shift to pairing operationwith a different parking space. Moreover, the parking space 32 after thecancellation of the pairing can shift to pairing with a differentvehicle.

[Description of Modifications of This Embodiment]

In the above-described embodiment, the description has been given of theexample where the subcoils SC1 to SC4 shown in FIG. 4 are mounted as thesubcoils provided at the bottom of the vehicle 20. Specifically, thedescription has been given of the example where mounted are the subcoilSC1 wound around the same core as the power reception coil 21, thesubcoil SC2 provided on the front side relative to the subcoil SC1, andthe subcoils SC3, SC4 provided on the left rear side and the right rearside relative to the subcoil SC1, respectively.

The present invention only requires at least one subcoil to be mountedon each of the front side and the rear side relative to the powerreception coil 21. Besides the subcoil arrangement shown in FIG. 4,arrangements shown in Parts (a) to (d) of FIG. 26 may be employed, forexample. Part (a) of FIG. 26 includes a subcoil SC2 provided on thefront side relative to the power reception coil 21 and a subcoil SC5provided on the rear side relative to the power reception coil 21. Also,no subcoil is mounted near the power reception coil 21. In other words,the subcoil SC1 shown in FIG. 4 is not mounted. A signal receivablerange QO is set around the power reception coil 21, a signal receivablerange Q2 is set around the subcoil SC2, and a signal receivable range Q5is set around the subcoil SC5.

In this case, the power reception coil 21 receives a pairing signaltransmitted from the power transmission coil 11 and acquires theidentification data. Specifically, when the signal receivable range Q0of the power reception coil 21 overlaps the excitation range of thepower transmission coil 11, the power reception coil 21 receives apairing signal transmitted from the power transmission coil 11. Then,the identification data contained in the pairing signal received by thepower reception coil 21 is acquired, and pairing is performed. Thissubcoil arrangement can also achieve advantegeous effects similar tothose by the above-described embodiment. Also, since the power receptioncoil 21 is used to acquire the identification data, the number ofsubcoils can be reduced.

Part (b) of FIG. 26 includes a subcoil SC1 wound around the same core asthe power reception coil 21, a subcoil SC2 provided on the front siderelative to the power reception coil 21, and a subcoil SC5 provided onthe rear side relative to the power reception coil 21. Moreover, asignal receivable range Q1 is set around the subcoil SC1, a signalreceivable range Q2 is set around the subcoil SC2, and a signalreceivable range Q5 is set around the subcoil SC5. This subcoilarrangement can also achieve advantegeous effects similar to those bythe above-described embodiment.

Part (c) of FIG. 26 includes a subcoil SC2 provided on the front siderelative to the power reception coil 21, subcoils SC3, SC4 provided onthe left rear side and the right rear side relative to the powerreception coil 21, respectively, and a subcoil SC6 provided rearward ofthe subcoils SC3, SC4. Moreover, a signal receivable range Q0 is setaround the power reception coil 21, a signal receivable range Q2 is setaround the subcoil SC2, a signal receivable range Q3 is set around thesubcoil SC3, a signal receivable range Q4 is set around the subcoil SC4,and a signal receivable range Q6 is set around the subcoil SC6. Thissubcoil arrangement can also achieve advantegeous effects similar tothose by the above-described embodiment.

Part (d) of FIG. 26 includes a subcoil SC2 provided on the front siderelative to the power reception coil 21 and subcoils SC3, SC4 providedon the left rear side and the right rear side relative to the powerreception coil 21, respectively. Moreover, a signal receivable range Q0is set around the power reception coil 21, a signal receivable range Q2is set around the subcoil SC2, a signal receivable range Q3 is setaround the subcoil SC3, and a signal receivable range Q4 is set aroundthe subcoil SC4. This subcoil arrangement can also achieve advantegeouseffects similar to those by the above-described embodiment.

Although the wireless power supply system and the wireless powerreception device of the present invention have been described based onthe illustrated embodiment, the present invention is not limited tothose. The configuration of each part can be replaced with anyconfiguration having a similar function.

For example, in the above-described embodiment, the description has beengiven of the example where the battery 23 is the electric load. However,the present invention is not limited to this example. For instance, anelectric motor can be the electric load.

REFERENCE SIGNS LIST

-   11, 11 a power transmission coil-   12 power unit-   13 ground controller-   14 communication unit-   15 dc power source-   20 vehicle-   21 power reception coil-   22 rectification-smoothing circuit-   23 battery-   24 vehicle controller-   25 communication unit-   31 inverter circuit-   32, 32 a parking space-   33, 33 a vehicle detection sensor-   51, 51 a ground unit-   61 ferrite core-   101 power transmission device-   102 power reception device

The invention claimed is:
 1. A wireless power reception device providedto a vehicle and configured to wirelessly receive power transmitted froma power transmission device provided on the ground, the wireless powerreception device comprising: a power reception coil configured to supplythe power received to the vehicle as drive force; at least one subcoilprovided on each of a front side and a rear side of the vehicle relativeto the power reception coil and configured to receive, as an excitationpattern signal, power transmitted from the power transmission coil ofthe power transmission device; a vehicle controller configured tocontrol power reception of the power reception coil and the subcoils;and a power-reception-side wireless device configured to communicatewith the power transmission device, wherein when the power transmissiondevice is excited using an excitation pattern signal containingidentification data, the vehicle controller acquires the identificationdata from the excitation pattern signal received by the subcoils, andtransmits the acquired identification data to the power transmissiondevice, the vehicle controller cancels pairing between the powertransmission coil and the power reception coil when the identificationdata received by the subcoil provided on the front side and theidentification data received by the subcoil provided on the rear sideare different from each other.
 2. The wireless power reception deviceaccording to claim 1, wherein two or more subcoils are provided on atleast one of the front side of the vehicle and the rear side of thevehicle relative to the power reception coil, and the vehicle controllercombines pieces of identification data detected by the two or moresubcoils provided on the at least one side of the vehicle, and transmitsthe combined pieces of identification data to the power transmissiondevice.
 3. The wireless power reception device according to claim 2,wherein the vehicle controller determines soundness of the combinedpieces of identification data, and does not transmit the combined piecesof identification data to the power transmission device if the combinedpieces of identification data is not sound.
 4. The wireless powerreception device according to claim 2, wherein the two or more subcoilsprovided on the at least one side of the vehicle have signal receivableranges which partially overlap each other and within which theexcitation pattern signal is receivable.